Microfluidic systems and control methods

ABSTRACT

The systems and methods disclosed herein include a microfluidic system, comprising a pneumatic manifold having a plurality of apertures, and a chip manifold having channels disposed therein for routing pneumatic signals from respective ones of the apertures to a plurality of valves in a microfluidic chip, wherein the channels route the pneumatic signals in accordance with a configuration of the plurality of valves in the microfluidic chip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuing application of U.S. Ser. No. 11/594,444filed on Nov. 8, 2006 and to U.S. Ser. No. 13/152,881 filed on Jun. 3,2011, both of which claim priority to Provisional Application No.60/760,552 filed on Jan. 19, 2006, the subject matter of all of whichare incorporated herein by reference in their entireties.

BACKGROUND

“Microfluidics” generally refers to systems, devices, and methods forprocessing small volumes of fluids. Because microfluidic systems canprocess a wide variety of fluids, such as chemical or biologicalsamples, these systems have many application areas, such as biochemicalassays (for, e.g., medical diagnoses), biochemical sensors, or lifescience research in general.

One type of microfluidic device is a microfluidic chip. Microfluidicchips may include micro-scale features (or “microfeatures”), such aschannels, valves, pumps, and/or reservoirs for storing fluids, forrouting fluids to and from various locations on the chip, and/or forreacting fluidic reagents. In some cases, microfluidic chips may includemore complex micro-scale structures such as mixing devices or sensorsfor performing other processing functions on the fluids. A microfluidicchip that integrates various microfeatures to provide various fluidprocessing functions is sometimes called a “Lab-on-a-chip.”

However, many existing microfluidic devices are prohibitively expensiveor prohibitively difficult to operate to be suitable for manyapplications. For example, many existing systems are too expensive to bedisposable or do not have enough programmed automation to be operated byan untrained field technician. Therefore, these systems cannot be usedin certain non-laboratory environments. Moreover, many microfluidicsystems are built for one specific application, and cannot be adapted orcustomized for other applications. Many microfluidic systems are notmodular, and therefore cannot benefit from the efficiencies ofmass-production or allow a user to reconfigure easily the system forvarious applications at hand.

Moreover, existing microfluidic systems lack adequate detection andanalysis systems. While microfluidic devices deliver higher processspeeds and require only small volumes of sample, these small volumes ofsamples are difficult to detect and analyze. By way of comparison, anexemplary non-microfluidic implementation is an Enzyme LinkedImmunosorbent Assay (ELISA), using a 96 well microplate with a welldiameter of 6 mm for the sample cuvet. In this case, the final volumefor a spectrometer measurement is around 100 .mu.l and corresponds to anoptical path length for an optical detector of about 4 mm. In contrast,a typical microfluidic channel or reservoir may have a channel depth ofless than about 100 microns. This optical path length is thus about40-fold lower than for a conventional microplate assay, which cancorrespond to a 40-fold decrease in detection signal intensity.

Furthermore, many existing detection systems do not adequately integrateto a microfluidic chip. As a result, an untrained technician may havedifficulty interfacing the microfluidic chip to the detector in order toprovide meaningful results. Finally, many existing systems use expensiveoptical components.

Thus, there exists a need for improved microfluidic systems forprocessing fluids, such as biological or chemical samples. It is desiredthat the systems are inexpensive and preferably disposable. It isdesired that the systems be simple to operate and that many orsubstantially all of the fluid processing steps be automated. It isdesired that the systems be customizable, and be modular such that thesystem can be easily and rapidly reconfigured to suit variousapplications. It is desired that the systems include integrateddetection systems which provide high detection sensitivity, but areinexpensive and preferably disposable.

SUMMARY

This invention, in various embodiments, addresses deficiencies in theprior art by providing microfluidic devices, systems, and methods. Thesystems and methods described herein include plastic microfluidic chipsthat route and process one or more reagents, along with manifoldstructures, controllers, and computers. Additionally, the systems andmethods include detectors and sensors for analyzing fluidic reagentsafter they have reacted.

More particularly, microfluidic chips described herein include variousmicroscale features (“microfeatures”) such as valves, pumps, channels,and reservoirs. These microfeatures are interconnected and allow forvarious combinations of fluid flow patterns that can be user specifiedand tailored to a specific application. In some implementations, thechip couples to a reagent cartridge or separate microfluidic reagentchip having reagent reservoirs. The chip's microfeatures transport oneor more reagents from respective reagent reservoirs, react the reagents,and transport the reaction products to outlet reservoirs. Detectors thenanalyze the reaction products.

Certain microfeatures on the chip, such as pumps and valves, areactively actuated by an external stimulus and thus may be referred to as“active” components. For example, in some implementations the pumps andvalves are pneumatically actuated. In certain implementations, a userspecifies a desired fluid flow pattern on the chip. In order topneumatically actuate the pumps and valves to produce the desired fluidflow pattern, the systems include a chip manifold for routing pneumaticsignals to appropriate pumps and valves, a pneumatic manifold havingpneumatic transducers coupled thereto for providing the pneumaticsignals to the chip manifold, a controller for actuating the pneumatictransducers according to programmed logic instructions, and a computerfor interfacing the controller and the user.

In one feature, the above-described systems are modular; they include apneumatic manifold that provides pneumatic signals and a separate chipmanifold that routes the pneumatic signals to appropriate pumps andvalves on the chip. This modular approach results in a reconfigurableand customizable system. More particularly, various applications maycall for various respective microfluidic chips. The systems describedherein allow a user to use a single computer, controller, and pneumaticmanifold for any of the various microfluidic chips, and the user needonly couple the pneumatic manifold to a chip manifold specific to aparticular chip at hand.

The invention also includes systems and methods for detecting,analyzing, and characterizing fluids. For example, systems describedherein include optical detector systems that measure the concentrationof an analyte in a fluidic sample. The optical detector systems canmeasure the concentration of several fluidic samples in parallel, andcan operate with high detection sensitivities in uncontrolledenvironments.

In one aspect, the above-described systems are inexpensive and may bedisposable. In certain embodiments, the microfluidic chips and manifoldsof this invention are made entirely from inexpensive plastic materials.In one embodiment, an entire microfluidic system that is suitable forportable immunoassay, including a chip, associated manifolds, andreagent cartridges or reagent chips, is made from polystyrene, whichresults in extremely low fabrication costs.

While certain fabrication methods may damage or distort microfeaturesformed within plastics, in certain implementations this invention usesweak-solvent bonding (e.g., acetonitrile solvent lamination methods).Weak-solvent bonding preserves the integrity and reliability of themicrofeatures disposed within the chips and manifolds. These aspects ofthe technology are described in U.S. patent application Ser. No.11/242,694, incorporated herein by reference in its entirety.Additionally, other aspects of the present invention can be used alone,or in combination with aspects of the inventions described in U.S.patent application Ser. No. 11/242,694.

Moreover, in certain embodiments the invention uses inexpensive buteffective equipment in place of other more expensive equipment known inthe art. For example, the invention uses inexpensive and disposableoptical detection systems in place of more complex and expensiveequipment used in commercial implementations.

In another aspect, the above-described systems are automated. Aprogrammable controller automatically drives solenoids, which transmitpneumatic signals through manifold structures. The manifold structuresroute the signals, which then actuate pumps and valves to transportfluid on the chip. By actuating the pumps and valves on the chip inspecific sequences, a user can efficiently perform a large number ofassays unattended.

Because the devices may have small dimensions, may be disposable, may becustomizable and reconfigurable, and may be automated, they provide aframework for offering inexpensive portable “Point-of-Care” (POC)systems with automated assay processing that can be run by users withlittle training.

In one aspect, the invention includes a microfluidic system, comprisinga pneumatic manifold having a plurality of apertures, and a chipmanifold having channels disposed therein for routing pneumatic signalsfrom respective ones of the apertures to a plurality of valves in amicrofluidic chip, wherein the channels route the pneumatic signals inaccordance with a configuration of the plurality of valves in themicrofluidic chip.

In one configuration, the chip manifold includes at least one set ofchannels for routing a pneumatic signal from one aperture of thepneumatic manifold to a plurality of the valves in the microfluidicchip. The at least one set of channels may comprise a single channel forrouting the pneumatic signal from the aperture to a plurality ofchannels branching from the single channel, wherein the plurality ofchannels branching from the single channel route the pneumatic signal torespective ones of the plurality of valves. Additionally oralternatively, the at least one set of channels may include a set ofchannels consisting of a single channel.

In one feature, the invention may include a plurality of microfluidicchips having different respective configurations of valves, andrespective chip manifolds corresponding to the plurality of microfluidicchips, wherein the respective chip manifolds have channels disposedtherein for routing pneumatic signals from at least some of theapertures of the pneumatic manifold to at least some of the valves oncorresponding ones of the associated plurality of microfluidic chips,and the channels of the respective chip manifolds route the pneumaticsignals in accordance with the respective configurations of theplurality of microfluidic chips.

In another feature, the systems may include a controller for controllingthe pneumatic signals being transmitted through the plurality ofapertures.

In one configuration, the plurality of apertures have respectivepneumatic transducers that fluidly couple to the plurality of aperturesfor transmitting the pneumatic signals through the plurality ofapertures, and the controller may be adapted to transmit electronicsignals that individually actuate the respective pneumatic transducersin a sequence according to logic instructions from the controller. Incertain configurations, the pneumatic transducers comprise solenoids.

According to one feature, at least one of the pneumatic transducers mayinclude an output port for transmitting a pneumatic pressure, and aswitch for selecting the pneumatic pressure as one of a positivepressure and a negative pressure, wherein the selecting is based on atleast one of the electronic signals. The pneumatic pressure supplied tothe output port may be generated by a DC-powered diaphragm pump that isdesigned to allow the portability of the microfluidic system. Thepneumatic manifold may further comprise attachment ports for couplingpneumatic transducers to the pneumatic manifold. The pneumatic manifoldmay include a plurality of laminated layers.

According to one configuration, the plurality of apertures haverespective pneumatic transducers that fluidly couple to the plurality ofapertures, the pneumatic manifold includes at least one positivepressure source and at least one negative pressure source, and the atleast one positive pressure source and the at least one negativepressure source fluidly couple to the pneumatic transducers. The atleast one positive pressure source may provide signals corresponding toa first state of binary logic communicated to the pneumatic transducersfrom a controller, and the at least one negative pressure source mayprovide signals corresponding to a second state of binary logiccommunicated from a controller to the pneumatic transducers.

In one feature, the microfluidic chip includes microfluidic pumps, andeach of the microfluidic pumps has three or more of the plurality ofvalves. The microfluidic chip may include a plurality of fluidicchannels for transporting and reacting fluidic reagents. Themicrofluidic chip may include reagent reservoirs for storing fluidicreagents, and outlet reservoirs for storing reaction products of thefluidic reagents.

According to another feature, the microfluidic system may comprise anoptical detection system for analyzing fluidic samples in themicrofluidic chip. The optical measurement system may include a lightsource for transmitting light through the fluidic reagent, and atransducer for receiving at least a portion of the transmitted light andproducing an electronic signal related to the strength of the receivedportion of the transmitted light. The optical detection system mayfurther include a slit disposed between the light source and thetransducer for attenuating ambient light. The optical detection systemmay include a band-pass filter disposed between the light source and thetransducer.

In certain configurations, each of the pneumatic manifold, the chipmanifold, and the microfluidic chip comprises a non-elastomer plasticmaterial. The non-elatomer plastic material may comprise at least one ofpolymethyl methacrylate, polystyrene, polycarbonate, and acrylic.

In one aspect, the invention includes a method of operating amicrofluidic system, comprising transmitting, by a pneumatic manifold,pneumatic signals to a chip manifold, routing, by the chip manifold, thepneumatic signals to a plurality of valves in a microfluidic chip, andactuating, by the pneumatic signals, the valves in the microfluidic chipto transport fluid through the microfluidic chip.

In certain implementations, the methods described herein may alsocomprise routing a pneumatic signal from one aperture of the pneumaticmanifold to a plurality of valves in the microfluidic chip.

In certain implementations, the methods may include activating, by aprogrammable controller, the sequence of pneumatic signals. The methodsmay include programming the controller with program logic instructions.

In certain implementations, the methods may include transmitting thepneumatic signals by switching, by a pneumatic transducer, between apositive pressure output and a negative pressure output in accordancewith the program logic instructions. Activating the sequence ofpneumatic signals may comprise transmitting electronic signals topneumatic transducers coupled to the pneumatic manifold, therebyactuating the pneumatic transducers.

In certain implementations, the methods may comprise transporting andreacting fluidic reagents in the microfluidic chip.

In one feature, the methods may include characterizing fluidic samplesin the microfluidic chip with an optical detection system.Characterizing the fluidic samples may comprise transmitting lightthrough the fluidic samples and detecting the amount of light allowed topass through the fluidic samples. Characterizing the fluidic samples mayfurther comprise filtering ambient light.

In another aspect, the invention includes a microfluidic system,comprising an array of pneumatic transducers, and a chip manifold havingchannels disposed therein for routing pneumatic signals from respectiveones of the pneumatic transducers to a plurality of valves in amicrofluidic chip, wherein the channels route the pneumatic signals inaccordance with a configuration of the plurality of valves in the chip.

The fluids described herein may comprise a liquid, a gas, a solid thatis substantially dissolved in a fluid material, a slurry material, anemulsion material, or a fluid material with particles suspended therein.“Reagents” generally refer to any materials, such as fluids, that reactto produce a reaction product. As used herein, a “pneumatic signal”generally refers to any sequence of air pressures, and a pneumatictransducer refers to any device that produces a pneumatic signal basedon an input, such as an electrical signal input.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages will be more fully understood bythe following illustrative description with reference to the appendeddrawings, in which like elements are labeled with like referencedesignations, and in which the drawings may not be drawn to scale.

FIG. 1A shows a schematic of a microfluidic system, according to anillustrative embodiment of the invention;

FIG. 1B illustrates a method of operation of the microfluidic system ofFIG. 1A, according to an exemplary use of the invention;

FIG. 2 shows a microfluidic chip assembly, according to an illustrativeembodiment of the invention;

FIGS. 3A-B show a reagent valve having a first substrate, a secondsubstrate, and a membrane, according to an illustrative embodiment ofthe invention;

FIGS. 4A-F show a channel pump including three valves, according to anillustrative embodiment of the invention;

FIG. 5 shows a bottom view of the microfluidic chip assembly of FIG. 2;

FIG. 6A shows a close-up of a top view of a pneumatic manifold includinga base, according to an illustrative embodiment of the invention;

FIG. 6B shows a close-up view of the pneumatic manifold and base of FIG.6A;

FIGS. 7A-D show a solenoid, according to an illustrative embodiment ofthe invention;

FIG. 8 shows an exemplary computer connected to the controller of FIG.1, according to an illustrative embodiment of the invention;

FIG. 9 shows an exemplary detection system, according to an illustrativeembodiment of the invention;

FIG. 10 shows a close-up side view of a detecting window and associateddetection components, according to an illustrative embodiment of theinvention;

FIG. 11 shows a more detailed front view of the detection system of FIG.9;

FIG. 12 shows a close-up front view of the detection componentsassociated with one exemplary detecting window, according to anillustrative embodiment of the invention;

FIG. 13 shows a top view of the detection components associated with theexemplary detecting window of FIG. 12;

FIG. 14 shows absorbance measurements of samples taken from anelectronic signal board, according to this experimental use of theinvention;

FIG. 15 shows a line plot of the absorbances of the samples of FIG. 14,set forth on a vertical axis, as a function of the concentration of thesamples, set forth on a horizontal axis;

FIG. 16 shows sample plots of absorbance as a function of concentrationaccording to an experimental use of the invention;

FIG. 17 shows sample plots according to an experimental use of theinvention wherein the fluidic samples have lower concentrations thatthose used for FIG. 16;

FIG. 18 schematically illustrates a two layer microfluidic structure ofa substrate and a deformable membrane, according to an exemplary aspectof the invention; and

FIG. 19 shows a schematic cross sectional view of a modular fluidiclayer as shown in FIG. 18 and a chip manifold manifold, according to anexemplary aspect of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The invention, in various embodiments, provides microfluidic devices,systems, and methods. The following detailed description of theinvention refers to the accompanying drawings. The following detaileddescription does not limit the invention. Instead, the scope of theinvention is at least the scope defined by the appended claims andequivalents.

FIG. 1A shows a schematic of a microfluidic system 100, according to anillustrative embodiment of the invention. The microfluidic system 100includes a microfluidic assay system 102, a computer 118, a computerdisplay 120, and an input device 122.

The microfluidic system 100 includes a microfluidic chip 104. Themicrofluidic chip 104 includes microfeatures such as channels, valves,pumps, and/or reservoirs for storing fluids, for routing fluids to andfrom various locations on the chip, and/or for reacting fluidicreagents. In order to route fluids through channels of the chipaccording to desired fluid flow patterns, the valves and pumps arepneumatically actuated in a certain sequence in accordance with thedesired fluid flow pattern.

The pneumatic signals that actuate the pumps and valves are generated byan array of pneumatic transducers 108, which couples to the chip 104 viamanifold structures 110. In the depicted embodiment, the array ofpneumatic transducers is a solenoid array 108. The manifold structures110 include a pneumatic manifold 110 a, which includes apertures fortransmitting pneumatic signals therethrough, and a chip manifold 110 b,for routing the pneumatic signals to appropriate pumps and valves on thechip 104. The microfluidic chip 104, the manifold structures 110, andthe solenoid array 108 will be described in more detail below.

The microfluidic assay system 102 also includes a diaphragm pump 126that supplies a positive and/or negative pressure to the solenoids inthe solenoid array 108. In addition, a controller 106 of themicrofluidic assay system 102 controls the pneumatic signals generatedby the solenoids in the solenoid array 108, and thereby controls theresulting fluid flow pattern on the chip 104. The computer 118 transmitscommands and/or programs to the controller 106. The input device 122 andthe display 120 interface the computer 118 and a user (not shown). Theinput device 122, the display 120, the computer 118, the controller 106and the diaphragm pump 126 will be described in more detail below.

The microfluidic assay system 102 also includes an optical detectionsystem 112 having a light source 114 and a detector 116 that analyzefluids on the microfluidic chip 104 (e.g., to analyze reaction products)using optical detection techniques. The optical detection system 112will be discussed in more detail below.

FIG. 1B illustrates a method of operation of the system 200, accordingto an illustrative embodiment of the invention. In use, a user firstinterfaces with the computer 118 via the input device 122 and thedisplay 120. The user provides instructions to the computer 118 (step280) related to the fluid processing functions (e.g., the reactionsamong reagents) that will take place on the chip 104. Next, the computer118 provides program logic instructions to the controller 106 (step282). However, in other exemplary methods the controller 106 ispre-programmed with logic instructions, as will be discussed in moredetail below. The controller 106 then transmits electronic signals tothe solenoids in the solenoid array 108 to actuate the solenoids insequences dictated by the program logic instructions (step 284). Thesolenoids, when actuated, transmit a sequence of pneumatic signalsthrough the pneumatic manifold 110 a to the chip manifold 110 b (step286). The chip manifold 110 b includes channels that route the pneumaticsignals to appropriate valves on the microfluidic chip (step 288). Thepneumatic signals then actuate the valves on the microfluidic chip 104(step 290), which transport and process fluid on the microfluidic chip104 (step 291) in accordance with the user's instructions to thecomputer 118.

In certain implementations, as mentioned above, the fluids are sample,and in some cases may be reagents that react on the chip. The user mayanalyze these fluidic samples and/or their reaction products. Moreparticularly, the user provides instructions to the computer 118 toactivate the optical detection system 112 (step 292). The opticaldetection system 112 analyzes the reaction products (step 294), andprovides the results of the analysis to the computer 118 which thendisplays the analysis results on the display 120 (step 296).

FIG. 2 shows a microfluidic chip assembly 200, according to anillustrative embodiment of the invention. The microfluidic chip assembly200 includes the microfluidic chip 104 and the manifold structures 110shown in FIG. 1, as well as a reagent cartridge 216 (not shown inFIG. 1) having a plurality of reagent reservoirs 214 that containfluidic reagents.

As mentioned above, the microfluidic chip 104 includes a plurality ofmicrofeatures, such as channels, valves, pumps, and/or reservoirs, forstoring fluids, for routing fluids to and from various locations on thechip, and/or for reacting fluidic reagents. By way of example, the chip104 includes a plurality of microfluidic channels 218, a plurality ofchannel pumps 222, a plurality of reagent valves 224, a dispensing valve226, a first set of reagent channels 228, a second set of reagentchannels 230, the reagent reservoirs 214, and the outlet reservoirs 220.The microfluidic channels 218, 228, and 230 can be of any suitabledimension, but in certain embodiments have cross-sectional diameters ofbetween about 1 micron and about 500 microns, or between about 1 micronand about 50 microns. The microfluidic chip 104 generally includes afirst substrate, and second substrate, and a membrane disposedtherebetween. The above-described microfeatures are fabricated withinone or more of the first substrate, the second substrate, and themembrane.

FIGS. 3A-B, by way of example, show a reagent valve 224 having a firstsubstrate 230, a second substrate 232, and a membrane 238. The reagentvalve 224 fluidly couples a reagent reservoir 214 to the channel 228.More particularly, each reagent reservoir 214 aligns with a respectivevalve 224. Fluid from the reagent reservoirs 214 flow into respectivereservoir ports 236. In one exemplary implementation, fluid flows from areagent reservoirs 214 in response to a user releasing a vacuumcondition in the reservoir 214, which allows the fluid to freely fallfrom the reagent reservoir 214 into the reservoir port 236. When thevalve 224 is actuated, the fluid in the reservoir port 236 flows to thechannel 228.

As mentioned, the valve 224 includes a first substrate 230, a secondsubstrate 232, and a membrane 238. The first substrate 230 has a drivechamber 234 fabricated therein. As depicted in FIG. 3A, a positivepneumatic force 235 through the drive chamber 234 closes the valve 224by pressing the membrane upwards against the second substrate 232,thereby cutting off (or substantially cutting off) fluidic communicationbetween the reservoir port 236 and the channel 228. In contrast, asdepicted in FIG. 3B, a negative pneumatic force 240 through drivechamber 234 opens the valve by drawing the membrane 238 away from thesecond substrate 232, thereby fluidly coupling the reservoir port 236 tothe channel 228. The depicted valve 224 is exemplary, and any valvestructure known in the art can be used with this invention.

In order for the membrane 238 to draw towards or away from the secondsubstrate 232, the membrane 238 is deformable. For example, the membrane238 has a Young's modulus of between about 2 Gpa and about 4 Gpa andhave a thickness, or width, selected for allowing deformation uponapplication of appropriate mechanical (e.g., pneumatic) force. Themembrane 238 has a thickness of between about 10 .mu.m and about 150.mu.m, or between about 15 .mu.m and about 75 .mu.m. The depicted firstsubstrate 230 and the depicted second substrate 232 each has a thicknesssubstantially larger than the thickness of the membrane 238, but inother implementations have thickness similar to or less than thethickness of the membrane 238.

According to an alternative exemplary aspect, the microfluidic chip 104(FIG. 2) may alternatively be constructed as including only a singlepolymeric substrate 232-1 similar to 232 in FIGS. 3A, 3B) and apolymeric membrane 238-1 (similar to 238 in FIGS. 3A, 3B) bondedthereto, to form fluidic layer 104-1, as illustrated in FIG. 18. Forsimplicity, substrate 232-1 is illustrated showing only two disconnectedmicrochannels (microfeatures) 1918 and an unbounded region in thesubstrate into which the diaphragm 238-1 can deflect when actuated toallow fluid transport between the channels, thus forming a diaphragmvalve as described herein throughout. According to this constructionalaspect, first substrate 230 (FIGS. 3A, 3B), is alternatively shown inFIG. 19 as a top layer 1930 (the surface that interfaces with the chip)of the chip manifold 110 b (FIG. 2; or the drive manifold 202 in FIG.5), or the chip manifold (e.g., 110 b, 202) itself. As furtherillustrated in FIG. 19, an optional sealing layer or gasket 1940 isdisposed on the top surface of, and becomes a component of, thealternative top layer of the chip manifold 1930. In either aspect, thepolymeric membrane 238-1 is interfaced against the top of the chipmanifold against either layer 1930 or alternatively against layer 1940to actuate diaphragm 238-1 in the operation of the device. Thus FIG. 19shows a modular microfluidic chip 104-1 operationally connected to achip manifold 1930 that includes an optional gasket 1940. A modularpneumatic manifold (e.g., 110 a in FIG. 2) would then be attached to thebottom side of chip manifold 1930.

Reservoirs (e.g., reagent reservoirs 214 in FIG. 2) may be provided asone or more attachable component(s) to the microfluidic chip 104-1 ormay be integrally disposed therein as a microfeature of the chip. Assuch, in the instant exemplary aspect, the modular microfluidic chip104-1 (fluidic layer) consists of a polymeric substrate including amicrofeature in a surface thereof, and a polymeric membrane (diaphragm)bonded to portions of the membrane surface containing the microfeature.Advantageously, the polymeric membrane is bonded to the substratesurface via a ‘weak solvent’ bonded process. The interested reader isdirected to U.S. Pat. Nos. 7,608,160 and 7,832,429, the disclosures ofwhich are incorporated herein by reference.

In addition to fluidly coupling a reservoir port 236 to a channel 228,other valves can additionally or alternatively fluidly couple two ormore channels to provide “one-to-many,” “many-to-many,” and/or mixingfunctionality. For example, referring again to FIG. 2, dispensing valve226 fluidly couples the first set of reagent channels 228 to the secondset of reagent channels 230. When only one of the first set of reagentchannels 228 includes fluid (because, e.g., only that channel'srespective valve 224 opens to port fluid from its respective reservoir214 while all other valves 224 remain closed), the dispensing valveprovides “one-to-many” reagent dispensing and processing. Namely, thecontents of one reagent reservoir 214 flow to many outlet reservoirs220. When a plurality of the first set of reagent channels 228 includefluid, the dispensing valve provides “many-to-many” reagent dispensingand processing. By selectively actuating certain ones of the reagentvalves 224 and the dispensing valve 226, an operator can mix selectedreagents from the reagent reservoirs 214 in the dispensing valve 226region before the mixture is pumped to the outlet reservoirs 220.

FIGS. 4A-F show a channel pump 222, according to an illustrativeembodiment of the invention. A microfluidic pump generally refers to anystructure or group of structures capable of applying pressure to a fluidand/or facilitating the flow of fluid in one or more desired directionsin a microfluidic device. The depicted pump 222 generally includes threevalves: an inlet valve 222 a, a drive valve 222 b, and an outlet valve222 c, interconnected by portions 218 b and 218 c of the microfluidicchannel 218. In operation, the pump 222 pumps fluid through themicrofluidic channel 218 by cycling through six states that areactivated sequentially to produce a peristaltic-like pumping effect.

More particularly, in FIG. 4A, the inlet valve 222 a opens and drawsfluid from an inlet portion 218 a of the microfluidic channel 218 intothe volume 252 between the membrane 238 and the second substrate 232. InFIG. 4B, the drive valve 222 b opens and draws more fluid into the pumpsystem. In FIG. 4C, the inlet valve 222 a closes. In FIG. 4D, the outletvalve 222 c opens. In FIG. 4E, the drive valve 222 b closes, and therebyforces fluid through the outlet valve 222 c and into an outlet portion218 d of the microfluidic channel 218. In FIG. 4F, the outlet valve 222c then closes. These six states complete one pump cycle, displacing avolume of fluid through the pump.

The pump 222 is bidirectional. If the cycle is reversed, portion 218 dis an inlet portion of the microfluidic channel 218, portion 218 a is anoutlet portion of the microfluidic channel 218, and fluid flows fromportion 218 d to portion 218 a.

The valve structures 222 a, 222 b, and 222 c are independentlyactuatable, in that any one of the valve structures can be actuated withlittle or substantially no effect on the state of the other valvestructures. Those skilled in the art will recognize that alternatesequences of states may produce a pumping effect, and that other pumpscan also be used with this invention.

Turning back to FIG. 2, we now describe exemplary fluid flow patterns onthe chip 104. As mentioned above, the reagent cartridge 216 includes aplurality of reagent reservoirs 214 that hold fluidic reagents. Thepumps and valves on the chip 104 generally transport fluid from thereagent reservoirs 214 to the outlet reservoirs 220 in accordance with auser-specified flow pattern.

More particularly, the chip 104 includes a plurality of reagent valves224 that align with the reagent reservoirs 214. As mentioned above, thereagent valves 224 release fluid from respective reagent reservoirs 214into respective microchannels 228 on the chip 104. A user may specifythat one, certain ones, or all of the reagent valves will open. Next,the dispensing valve 226 opens to fluidly couple the first set ofreagent channels 228 and the second set of reagent channels 230. Thefluid from the first set of reagent channels 228 then flows to thesecond set of reagent channels 230. Next, the pumps 222 transport thefluid along the microfluidic channels 218. The user may specify thatone, certain ones, or all of the pumps 222 transport the fluid.

In some cases, the fluids stored in the reagent reservoirs 214 will bereagents that chemically react with other reagents on the chip 104. Forexample, a user may specify that the reagent in a certain reservoir 214will react with another reagent in another reservoir 214, in which casethe corresponding reagent valves 224 and the dispensing valve 226 willactuate to mix the reagents, as was described above.

The reagents may also mix and react in the microfluidic channels 218.Moreover, additionally or alternatively, the microfluidic channels 218themselves may include reagents. The reagents may be disposed in themicrofluidic channels 218 in a number of forms. By way of example, themicrofluidic channels 218 may include an insert strip (e.g., an insertmembrane strip) with reagents coated or adhered thereto. In otherimplementations, the microfluidic channels 218 may include small spheres(i.e., sphereoids or microspheres) coated with reagents.

For example, in one use the chip 104 performs a biological or chemicalassay. In this use, the reagents in the microfluidic channels 218 arevarious biological and/or chemical samples. The reagent reservoirs 214may include one or more of buffer wash, antibody, antibody withconjugated enzyme, and enzyme substrate. The contents of the reagentreservoirs 214 are released according to a user-specified sequence. Theorder and timing of release of the reagents from their respectivereagent reservoirs 214 correspond to the steps of the particular assaymethod being used.

It may be desirable to allow these chemical reactions to incubate forlonger periods of time within the microfluidic channels 218 by passingthe fluids through the microfluidic channels 218 multiple times. Asmentioned above, the channel pumps 222 can pump fluids bi-directionally,which allows back-and-forth fluid flow along the microfluidic channels218. The bidirectional pumping repeatedly moves a reagent back 260 andforth 262 along the channels 218 to provide longer reaction time andgreater reaction efficiency.

During these back-and-forth pumping cycles, air bubbles may form in thechannels 218. The ventilation valves 264 and 266 vent the air bubbles toambient air. Optionally, the outlet reservoirs 220 may also vent toambient air to release the air bubbles.

Other fluid flow patterns are also possible. More particularly, byselectively operating the reagent valves 224, the distribution valve226, and the channel pumps 222, fluid can flow in various combinationsof flow patterns from the reagent reservoirs 214 to the outletreservoirs 220. In particular, one or more specific reagents stored inthe reagent reservoirs 214 may be selectively dispensed into assaychannels at user-specified rates, in user-specified amounts, and atuser-specified times, and then can be incubated in the channel and thenstored and analyzed in the outlet reservoirs 220. Moreover, othermicrofluidic chip layouts with alternative configurations of valves,pumps, and reservoirs, may be used.

With continued reference to FIG. 2, the pneumatic forces described abovethat actuate the valves and pumps on the microfluidic chip 104 areprovided by an array of solenoids that transmit pneumatic signals. Thesolenoids (not shown in FIG. 2, and to be described in more detailbelow) are located generally within and/or under the pneumatic manifold110 a, and attach to the pneumatic manifold 110 a via attachment ports(not shown in FIG. 2) that will be described below. Each solenoidpneumatically couples to a respective aperture 270-281 and transmitspneumatic signals therethrough. In one exemplary implementation, eachsolenoid transmits a pneumatic signal that comprises positive pressurecorresponding to the positive pneumatic force 235 of FIG. 3A, negativepressure (e.g., vacuum pressure) corresponding to the negative pneumaticforce 240 of FIG. 3B, and/or sequences of positive and negativepressure.

The pneumatic signals are transmitted through the apertures 270-281 ofthe pneumatic manifold 110 a to pneumatic ports 283-294 on the undersideof the chip manifold 110 b. The pneumatic ports 283-294 fluidly coupleto pneumatic channels which route the pneumatic signals to appropriatepumps and valves on the chip 104. By way of example, aperture 276transmits a pneumatic signal to pneumatic port 283. This pneumaticsignal is transmitted through the pneumatic channel 304 to a pluralityof valve ports 308. These valve ports 308 provide the positive ornegative pneumatic force of the pneumatic signal to the valves 222 c ofthe channel pumps 222. Similarly, the aperture 271 transmits a pneumaticsignal to the pneumatic port 290, which fluidly couples to a channel306. The channel 306 routes the pneumatic signal to the valve ports 310.The valve ports 310 provide the positive or negative pneumatic force, asthe case may be, to the drive valves 222 b of the channel pumps 222.Likewise, the aperture 270 transmits a pneumatic signal to the pneumaticport 289, which fluidly couples to a channel 314. The channel 314 routesthe pneumatic signal to the valve ports 312. The valve ports 312 providethe positive or negative pneumatic force, as the case may be, to thevalves 222 a of the channel pumps 222.

As illustrated, the pneumatic signal from one solenoid (e.g., thesolenoid coupled to aperture 270) may be routed to actuate several valvestructures (e.g., the valves 222 a). In the depicted exemplaryimplementation, by cycling the three solenoids that couple to apertures270, 271, and 276 through positive pneumatic force and negativepneumatic force states appropriately, all of the channel pumps 222operate simultaneously. However, in other implementations, certainchannel pumps 222 may be independently actuatable by respectiveindependent solenoids.

The above described aperture 270 actuates a plurality of valves 222 a byrouting a pneumatic signal along a single pneumatic channel 314. Inother cases, an aperture may actuate a plurality of valves by routingthe signal along multiple pneumatic channels. By way of example, severalpneumatic channels may couple to a single pneumatic port, and route apneumatic signal to several respective valve ports. Alternatively, asingle pneumatic channel coupled to a single pneumatic port may branchinto a plurality of channels that couple to respective valve ports.

Other solenoids actuate only one valve. For example, the solenoidcoupled to aperture 279 transmits a pneumatic signal to the pneumaticport 286, which couples the signal to the channel 320 to route thesignal to the valve port 322. As depicted, this pneumatic signal fromaperture 279 actuates only one of the reagent valves 228.

Thus, as depicted, the chip manifold 110 b includes channels that routepneumatic signals in accordance with a configuration of the valves inthe microfluidic chip 104. Therefore, if a different application calledfor a replacement microfluidic chip with a different configuration ofvalves, then the user would only need to include a replacement for thechip manifold 110 b that includes channels which route pneumatic signalsin accordance with the configuration of valves on the replacementmicrofluidic chip. The user can continue using the other components ofthe microfluidic system 100, including the pneumatic manifold 110 a, thecontroller 106, etc. This provides for an easily reconfigurablemicrofluidic system 100.

FIG. 5 shows a bottom view of the microfluidic chip assembly 200. Inaddition to the chip 104, the reagent cartridge 216, and the chipmanifold 202, FIG. 4 shows the pneumatic manifold 204 including a base326 for mounting the solenoids to the pneumatic manifold 204, and forrouting positive and negative pressure to and from the solenoids.

For each of the apertures 270-281 depicted in FIG. 2, the base 326includes a plurality of corresponding ports. By way of example, for thedepicted aperture 270, the base 326 includes: attachment ports which aredepicted as the two mounting ports 328 (e.g., threaded screw slots) forattaching a solenoid (not shown) to the base 326, a pressure port 330for providing a positive pressure to the solenoid, a vacuum port 332 forproviding a negative (e.g., vacuum) pressure to the solenoid, and anoutput port 334 for switcheably outputting one of the negative pressureand the positive pressure from the solenoid depending on an electricalsignal transmitted to the solenoid from the controller 106.

FIG. 6A shows a close-up of a top view of the pneumatic manifold 204 andthe base 326, and FIG. 6B shows a close-up view of FIG. 6A. The base 326includes two layers, a bottom layer 336 and a top layer 338. Asmentioned above, the mounting ports 328 are used to attach a solenoid tothe base 326. In one implementation, the mounting ports 328 are threadedscrew slots, and the solenoid (not shown in FIGS. 6A-B) include screwsthat mate with the threaded screw slots. In the depicted embodiment, themounting ports 328 span the width 336 a of the bottom layer 336, but inother implementations may also extend through all or a portion of thetop layer 338 and/or the through all layers of the pneumatic manifold204.

As mentioned, the pressure port 330 provides a positive pressure to thesolenoid and the vacuum port 332 provides a negative pressure to thesolenoid. These pressures are provided, respectively, by a positivepressure source, depicted as the pressure inlet 340, and a negativepressure source, depicted as the vacuum inlet 342. In particular, adiaphragm pump 126, as depicted in FIG. 1, couples to the pressure inlet340 and transmits a positive pressure therethrough. The pressure line344 routes this pressure to the pressure port 330. Similarly, adiaphragm pump 126 couples to the vacuum inlet 342 and transmits anegative pressure therethrough. The vacuum line 346 routes this negativepressure to the vacuum port 332. In certain examples, diaphragm pumps126 are small in size and are DC-powered so as to facilitate theportability of the microfluidic system 100. Accordingly, in certainembodiments, the systems may include a portable power supply, such as abattery or battery pack or solar cells that provides sufficient power tooperate the DC powered diaphragm pump. The batteries may be rechargeableand in certain optional embodiments, the battery or battery pack may beincorporated into a power circuit that allows for battery operation oroperation from wall current. Such power supply systems are known in theart and suitable power supply circuits may be employed without departingfrom the scope hereof.

In the depicted embodiment, the pressure inlet 340 extends through thewidth 336 a of the bottom layer 336, while the vacuum inlet 342 extendsthrough the width 336 a and the width 338 a of both the bottom layer 336and the top layer 338, respectively. This may be beneficial so that thevacuum line 346 and the pressure line 344 can route pneumatic pressure(negative or positive, as the case may be) to the various pressure portsand vacuum ports of the base 326 without interfering with each other.

As mentioned above, the solenoid (not shown) switcheably selects eitherthe negative pressure provided by the vacuum line 346 or the positivepressure provided by the pressure line 344 depending on an electricalsignal transmitted to the solenoid from the controller 106. The solenoidtransmits the selected pressure through a solenoid output port 334. Thedepicted solenoid output port 334 extends through the bottom layer 336and the top layer 338, and couples to the aperture 270 of the pneumaticmanifold 204. As mentioned above, the aperture 270 then couples to thepneumatic port 289.

While the above-description was with respect to the exemplary aperture270 and the associated ports 328, 330, 332, and 334 on the base 326,similar port structures switcheably provide positive or negativepneumatic pressure from respective solenoids through respectiveapertures 270-276 to respective pneumatic ports 283-294.

FIGS. 7A-D show a solenoid 600, according to an illustrative embodimentof the invention. More particularly, FIG. 7A shows a front view, FIG. 7Bshows a side view, FIG. 7C shows a top view, and FIG. 7D shows aschematic representation of the solenoid 600. While the depictedembodiment uses solenoids such as solenoid 600, any other type ofpneumatic transducer may be used.

As mentioned above, the solenoid 600 mounts to the base 326 via screwslots 328. The solenoid 600 includes mounting screws 612 which couple tothe screw slots 328. The mounting screws include rotatable screw heads613 that can be rotated by, e.g., a screw driver or a user's fingers.

Also as mentioned above, the solenoid 600 receives a positive pressurefrom the pressure inlet 340 via the pressure line 344, and a negativepressure from the vacuum inlet 342 via the vacuum line 346. The solenoidincludes a pressure input 610 and a vacuum input 608 to receive theserespective pressures.

Moreover, as mentioned above the solenoid 600 transmits either thepositive pressure or the negative pressure, depending on an electricalsignal transmitted to the solenoid 600 from the controller 106. Thus,the solenoid includes an electrical coupler 616 which in this embodimentis a standard two-pin plug. The controller electrically couples to thesolenoid 600 via a cable having a socket for interfitting with the plug616.

The solenoid 600 transmits the positive or negative pressure from eitherthe vacuum input 608 or the pressure input 610, as the case may be,through the solenoid output 606 (e.g., an output port). FIG. 7D depictsthe manner in which the solenoid 600 switches between the positivepressure and the negative pressure. In one embodiment, as illustrated bysolenoid 600 a of FIG. 7D, the pressure port 610 is connected to theoutput port 606 to transmit a positive pressure. In this case, air tendsto flow from the pressure port 610 to the output port 606 as indicatedby arrow 620 a. In another embodiment, as illustrated by solenoid 600 b,the vacuum port 608 is connected to the output port 606 to deliver anegative pressure flow. In this mode of pressure transmission, air tendsto flow from the output port 606 to the vacuum port as indicated byarrow 620 b. In certain embodiments, the output 606 transmits a positivepressure having a magnitude of less than about 50 psi, or between about3 psi and about 25 psi, and a negative pressure having a magnitude ofless than about 15 psi, or between about 3 psi and about 14 psi.

As described, the controller 106 transmits electronic signals thatindividually actuate respective solenoids (e.g., solenoid 600) in asequence according to logic instructions. To do this, the controller 106transmits electrical signals that actuate the solenoids (e.g., solenoid600) to transmit either positive pressure or negative pressure. In oneimplementation, as discussed above, the controller 106 transmits theelectrical signals in accordance with serial logic instructions from thecomputer 118. In another implementation, the controller 106 includes amemory that includes programmed logic instructions. In this case, thecontroller 106 need not be coupled to a computer 118.

In either case, the controller 106 translates the instructions toelectronic signals that switch solenoids between positive pressure andnegative pressure. In one implementation, the logic instructionscomprise object-oriented source code including hierarchically relateddata structures, with each data structure corresponding to a particulartype of instruction. The program logic instructions may reference datastructures that comprise states of particular valves, data structuresthat comprise cycles of the states, and data structures that comprisesequences of the cycles.

For example, with continued reference to FIG. 2, the logic instructionsmay include instructions to shuttle fluid back and forth along amicrofluidic channel 218. In order to do this, the logic instructionsmay define certain states for each of the valves 222 a, 222 b, and 222 cof the channel pumps 222. One exemplary set of states includes twostates of binary logic, namely ‘+’ corresponding to an ‘open valve’instruction, and ‘−’ corresponding to a ‘close valve’ instruction. Thus,for the valves 222 a-c, a list of states may include: {+222 a, +222 b,+222 c, −222 a, −222 b, −222 c}. The labeling of these states isexemplary, and the logic instructions may use other references for thestates.

In other implementations, the chip 104 may include 3-way valves thatswitcheably couple any two or more of three microfluidic channels. Inthis case, there may be five states of logic for the valve: one whereinno channels couple, one wherein all three of the channels couple, andthree corresponding to the various combinations in which two of thethree channels couple. This can be extended to valves that switcheablycouple any number of channels.

Returning to the exemplary channel pumps 222, a forward-pumping cyclemay be defined based on the valve states as:Pump Forward=[+222a, +222b, −222a, +222c, −222b, −222c]which corresponds to the exemplary pumping cycle illustrated in FIG. 4.Similarly, a backward-pumping cycle may be defined as:Pump Backward=[+222c, +222b, −222c, +222a, −222b, −222a].

A shuttle sequence may be defined based on these pumping cycles as:Shuttle Fluid=[Pump Forward, Pump Backward, Pump Forward, Pump Backward,Pump Forward, Pump Backward, Pump Forward]

While the logic instructions may be implemented on the controller 106using source code instructions such as those given above, the controllermay additionally or alternatively use other implementations. By way ofexample, the controller may codify the logic instructions using one ormore of programming languages based on C, C++, C#, COBOL, BASIC, Java®,assembly language, and like computer program languages.

As mentioned above, in some implementations the logic instructions arestored in a memory of the controller 106. They may be transferred intothe memory from a computer (e.g., computer 118) using any suitablenetwork connection, or programmed directly into the controller 106. Alsoas mentioned above, in other implementations the logic instructions aretransmitted serially to the controller 106 from the computer 118.

FIG. 8 shows an exemplary computer 118 connected to the controller 106,according to an illustrative embodiment of the invention. The exemplarycomputer system 118 includes a central processing unit (CPU) 702, amemory 704, and an interconnect bus 706. The CPU 702 may include asingle microprocessor or a plurality of microprocessors for configuringcomputer system 118 as a multi-processor system. The memory 704illustratively includes a main memory and a read only memory. Thecomputer 118 also includes the mass storage device 708 having, forexample, various disk drives, tape drives, etc. The main memory 704 alsoincludes dynamic random access memory (DRAM) and high-speed cachememory. In operation, the main memory 704 stores at least portions ofinstructions and data for execution by the CPU 702.

The mass storage 708 may include one or more magnetic disk or tapedrives or optical disk drives, for storing data and instructions for useby the CPU 702. The mass storage system 708 may also include one or moredrives for various portable media, such as a floppy disk, a compact discread only memory (CD-ROM), or an integrated circuit non-volatile memoryadapter (i.e. PC-MCIA adapter) to input and output data and code to andfrom the computer system 118.

The computer system 118 may also include one or more input/outputinterfaces for communications, shown by way of example, as interface 710for data communications to the controller 106. The data interface 710may be a modem, an Ethernet card or any other suitable datacommunications device. The data interface 710 may provide a relativelyhigh-speed link to a network, such as an intranet, internet, or theInternet, either directly or through an another external interface (notshown). The computer 118 may connect to the network, and communicate tothe controller 106 when the controller 106 connects to the same network.The link may be, for example, optical, wired, or wireless (e.g., viasatellite or cellular network). Alternatively, the computer system 118may include a mainframe or other type of host computer system capable ofWeb-based communications via the network. The data interface 710 allowsfor delivering content, and accessing/receiving content via the network.

The computer 118 also couples to suitable input/output ports forinterconnection with the display 120 and the keyboard 122 or the likeserving as a local user interface for programming and/or data retrievalpurposes. Alternatively, server operations personnel may interact withthe computer 118 for controlling and/or programming the system fromremote terminal devices via a network, such as the exemplary networksdiscussed above.

The computer system 118 may run a variety of application programs andstores associated data in a database of mass storage system 708.

The components contained in the computer system 118 are those typicallyfound in general purpose computer systems used as servers, workstations,personal computers, network terminals, and the like. In fact, thesecomponents are intended to represent a broad category of such computercomponents that are well known in the art.

While the above description was given in connection with the computer118, it may also apply to the controller 106. More particularly, thecontroller 106 may include all or some of the components of the computer118 described in connection with FIG. 8.

As mentioned above, in certain implementations the fluids are reagentsthat react on the chip, and the user then analyzes the reactionproducts. By way of example, the reagents may react in the microfluidicchannels 218 using the bi-directional pumping of the channel pumps 222,after which the channel pumps 222 transport the fluid into the outletreservoirs 220. The optical detection system 112 analyzes the reactionproducts as they flow to the outlet reservoirs 220.

FIG. 9 shows an exploded view of an exemplary detection system 800similar to the optical detection system 112 of FIG. 1, according to anillustrative embodiment of the invention. More particularly, the system800 includes a microfluidic chip 801, similar to the microfluidic chip104 of FIG. 1, a light housing 804, and a detector assembly 805. Thedepicted detection system 800 analyzes reaction products by detectinganalyte concentrations of the reaction products.

The microfluidic chip 801 includes a plurality of microfluidic channels816 that transport fluid to outlet reservoirs 828. The microfluidicchannels 816 are similar to the microfluidic channels 218, but havewinding portions 816 a having a plurality of curves. The plurality ofcurves increase the distance that reagents must flow along themicrofluidic channels 816 when compared to linear channels (e.g.,microfluidic channels 218). This may be beneficial when fluidic reagentsare reacting in the channel 816, since the reagents take a longer amountof time to travel the increased distance, and this increases thereaction incubation time.

Before entering the outlet reservoir 828, the fluid flows through adetecting window 814 where it is characterized by the detection system800. Generally, the detection system 800 in the depicted implementationcharacterizes the fluid in the detection window 814 by measuring itsinteraction with light. The light housing 804 includes light sources 802that transmit light through the detecting window 814. The detectorassembly 805 includes photodiodes 824 that receive the light after it istransmitted through the detecting window 814, and output signals relatedto the amount of light they receive. These signals are mapped intoanalyte concentration measurements.

More particularly, if a detecting window includes a fluid with a highanalyte concentration, more of the light will be absorbed by the analyteand the output signal of the photodiode 824 will be lower. Thus, basedon the output signal of the photodiode 824, the system 800 quantifiesthe absorbance of the sample, and either directly uses the absorbance asa measure of the analyte concentration, or maps the absorbance into anactual analyte concentration (e.g., a relative concentration).

More particularly, the absorbance value A of sample at a specificwavelength of light can be given by Beer's Law:A=□/cwhere c represents the concentration c of the analyte's molecule, lrepresents the optical path length (i.e., the distance of the detectingwindow 814 through which the light travels), and □ is a constant ofproportionality referred to as absorptivity or molar extinctioncoefficient if the concentration is measured in moles/liter.

The absorbance value A of a sample can be measured from the outputsignal of the photodiode 824 as:A=−log((I _(s) −I _(d))/(I _(r) −I _(d)))where I_(s) represents the output signal of the photodiode 824 inresponse to the sample being measured, I_(d) represents the outputsignal of the photodiode 824 under dark conditions, and I_(r) representsthe output signal of the photodiode 824 in response to a referencefluid. The absorbance A can then, optionally, be mapped to aconcentration c using Beer's Law (Equation (1)).

More particularly, the light housing 814 includes a plurality ofapertures 806, in which the light sources 802 are disposed. The lightsources 802 align with respective detecting windows 814 and transmitlight therethrough. In one implementation, the light source is an LEDwith a spectral half width of less than about 60 nm. However, othertypes of light sources may be used. In particular, the light sources maytransmit light of various wavelengths (e.g., the light need not bevisible), with various intensities, and with various polarizationcharacteristics. In one use, the light has at least sufficient intensitysuch that at least some of the light transmits entirely through thedetection window 814 in detectable amounts.

In certain embodiments, each of the light sources 802 is adjustable. Thelight sources 802 may be collectively adjustable, so that a techniciancan optimize the performance of the system 800. The light sources 802may, additionally or alternatively, be individually adjustable, so thata technician can further adjust individual ones of the light sources 802to further optimize the performance of the system 800. Exemplaryadjustable parameters includes intensity, wavelength, bandwidth, andpolarization.

As mentioned, the light sources 802 transmit light through the detectingwindow 814. The light is then detected by the detector assembly 805. Inparticular, the detector assembly 805 includes a photo-mask 818 having aplurality of viewing slits 820. The photo-mask attenuates (oreliminates) ambient light so that the ambient light does not interferewith detections of the light transmitted by the light source 802. Moreparticularly, the viewing slit 820 is depicted as a narrow and elongateslot, and attenuates stray, broad spectrum light. As a result, when thedetector is placed in an uncontrolled environment, such as a lightedroom or an outdoor environment with variable ambient lighting, theoutput signal of the photodiode I_(s) is not distorted by the varyingambient light. In other embodiments, instead of a slit 820, thephoto-mask 818 may include other configurations of apertures.

The detector assembly 805 also includes band-pass filters 822. Theband-pass filters 822 also serve, in part, to filter out ambient light.Thus, in certain implementations, the band-pass filters 822 are tuned tosubstantially similar wavelength ranges as the light sources 802.

The band-pass filters 822 also serve to maintain a linear relationshipbetween the concentration of the analyte and the absorbance A as it iscalculated based on the output signal of the photodiode 824. This linearrelationship may be beneficial for a variety of reasons, includinganalytical simplicity and reproducibility and standardization ofanalytical results.

More particularly, as indicated above with respect to Equation (1), theabsorbance of a sample is linearly related to the concentration of thatsample for a particular wavelength. However, as mentioned above, thelight sources 802 may transmit light having a bandwidth substantiallywider than just a single wavelength. Thus, the linear relationship ofEquation (1) may not hold. Therefore, in certain embodiments, theband-pass filters 822 are monochromators that pass-through only a singlewavelength (e.g., a technician-selected wavelength) of the light fromthe light sources 802. However, in certain cases a monochromator may beprohibitively large and/or expensive. Thus, the band-pass filters 822may comprise smaller and/or more inexpensive filters having wider passbands that provide a sufficiently linear relationship between a sample'sabsorbance and its analyte concentration. The passband may be less thanabout 20 nm, less than about 10 nm, or less than about 5 nm.

Light that travels through the band-pass filters 822 is detected by thephotodiodes 824. The photodiodes may comprise any photodiode variationknown in the art. In one aspect, the photodiodes include built-intrans-impedance amplifiers which provide increased detectionsensitivity.

The increased detection sensitivity may be desired because, in certainexemplary uses, varying analyte concentrations in the fluid samplesresult in only small variations in light intensities at the photodiodes824. In order to amplify these small variations, the photodiode may usefeedback resistors with high resistances (e.g., more than about 300 Mohmor more than about 400 Mohm). In some implementations, the photodiodemay includes a discrete component operational amplifier in combinationwith the feedback resistors, but this may result in slow responses,signal distortion, and channel-to-channel variability. Therefore, inother implementations, the photodiode comprises a CMOS integratedphotodiode in combination with a trans-impedance amplifier, which canprovide high detection sensitivity and low fabrication costs. Althoughthe above-description is with respect to the photodiodes 824, anysuitable transducer may be used in their place.

FIG. 10 shows a close-up side view of a detecting window 814, accordingto an illustrative embodiment of the invention. As shown, themicrofluidic chip 801 includes a top substrate 808, a bottom substrate812, and a membrane 810 disposed therebetween. The detecting window 814is formed within the top substrate 808 of the microfluidic chip 801. Thedetecting window 814 couples to a microfluidic channel 816, whichtransfers fluid to the detecting window 814, and to a waste/outletreservoir 828, which receives the fluid after it is detected.

As shown, the detecting window 814 has larger dimensions (e.g.,cross-sectional height and width) than the channel 816. This may bebeneficial for several reasons. A detecting window 814 that is too smallmay result in undetectable signals from the photodiode 824. A largerdetecting window 814 allows more of the sample in the detecting window814, and can result in more detection sensitivity.

Additionally, a larger detecting window 814 results in a greater opticalpath length 814 a, which also improves the detection sensitivity. Moreparticularly, as mentioned above with respect to Beer's Law (Equation(1)), the absorbance A of a sample is linearly related to the opticalpath length 814 a, denoted as 1 in Equation (1). Therefore, a largeroptical path length 814 a results in larger magnitudes of change in theabsorbance A for a given change in concentration c. The largermagnitudes of change are easier for the photodiode 824 to detect, andthereby result in increased detection sensitivity.

While a larger detecting window 814 has benefits, in certainimplementations the volume of the detecting window 814 is kept withincertain limits. If the volume of the fluid in the detecting window 814deviates significantly from the volume of the fluid processed in thechannel 816, the detector's performance may degrade. By way of example,a very large detecting window 814 may prolong the concentration balancetime (i.e., the time required for the concentration of the analyte tosubstantially homogenize throughout the sample).

While various dimensions may be suitable in view of the aboveconsiderations, in certain embodiments the channel 816 has across-sectional height of between about 1 micron and about 50 microns,or between about 3 microns and about 20 microns, while the detectingwindow 814 has a cross-sectional height 814 a of between about 50microns and about 750 microns.

In addition to its size, the orientation of the detecting window 814improves the detection sensitivity of the system 800. In the depictedconfiguration, the light source 802 and the photodiode 824 are orientedalong an axis perpendicular to the main plane of the chip 801 and thedetecting window 814. This perpendicular orientation may be beneficialso a technician does not need to realign the photodiodes 824, detectingwindows 814, and light sources 802. More particularly, in oneimplementation the distance between the light sources 802 and thephotodiodes 824 is adjustable by, e.g., adjusting the vertical distancebetween the light sources 802 or the photodiodes 824 and the chip 801.As a result of the perpendicular orientation, a technician can easilyvertically adjust the light sources 802 and/or the photodiodes 824 tooptimal locations without having to realign them with the detectingwindow 814.

FIG. 11 shows a more detailed front view of the detection system 800. Asdepicted in previous figures, FIG. 11 shows the light sources 802, thedetecting windows 814, the photo-mask 818 with slits 820 disposedtherein, the band-pass filters 822, and the photodiodes 824.

Also shown is a voltage source labeled as V+, and electrical groundlabeled as V−, both of which couple to the light sources 802 in order toprovide a voltage differential that powers the light sources 802. Thevoltage differential may come from any suitable source, such as anelectrical wall outlet, a battery, or a fuel cell (e.g., a micro-fuelcell). Each of the light sources couples to the voltage source V+through a series connection with a current-limiting adjustable resistor1002. The adjustable resistors 1002 can be individually adjusted toalter the amount of current driving the respective light sources 802 andthereby alter the intensity of the light source 802. In use, atechnician calibrates the resistance of each of the resistors 1002 inorder to compensate for manufacturing variations and other sources ofvariation in the light sources 802, the band-pass filters 822, thephotodiodes 824, the detecting windows 814, or any of the othercomponents described herein.

More particularly, in one use the technician fills each of the detectingwindows 814 with a common reference buffer. The technician then powersthe light sources 802 and monitors the output signals from thephotodiodes 824. These reference output signals were described above inconnection with Equation (2) and referred to as I_(r). The manufactureradjusts each of the adjustable resistors 1002 so that the correspondingoutput signal I_(r) is substantially as high as can be achieved withoutsaturating the corresponding photodiode 824. Since I_(d) is acharacteristic constant of the photodiode under “dark” conditions andits value is often significantly smaller than I_(r) for a given systemnoise level, maximizing I_(r) can improve the signal/noise ratio of theoutput signal of the photodiode 824 and increase the dynamic range ofthe detections. However, other methods for calibrating the resistors1002 may also be used. For example, a digital to analog converter isused with a computer control to automate the calibration process.

FIG. 12 shows a close-up front view of the detection componentsassociated with one exemplary detecting window 814, according to anillustrative embodiment of the invention. As shown, a chamber 825tightly fits therein the photodiode 824 and the band-pass filter 822.The band-pass filter 822 is substantially coplanar with the surface 805a of the detector assembly 805 and is substantially perpendicular to theviewing slit 820. The viewing slit 820 has a smaller lateral dimensionthan the detecting window 814, so that the entire open area of theviewing slit 820 is completely covered by the detecting window 814 (aswill be shown more clearly in a subsequent figure). This ensures thatthe light that passes through the sample in the detecting window 814 ismeasured by the photodiode 824, while ambient light is attenuated. Thelight that passes through the detecting window 814, the viewing slit820, and the band-pass filter 822 is then received by the photodiode824. In the depicted embodiment, the photodiode 824 includes a sensingelement 827 which detects the light.

FIG. 13 shows a top view of the detection components associated with oneexemplary detecting window 814. As shown, the detecting window 814completely covers the viewing slit 820. Also shown is the band-passfilter 822 and the sensing element 827.

Exemplary experimental results are now described in connection withFIGS. 14-18. In the experiment, eight fluid samples were transported ona microfluidic chip (similar to chips 104 and 801) through eightrespective microfluidic channels and into corresponding detectingwindows.

The detection components used for the detecting windows included LEDshaving peak emissions of 430 nm, bandpass filters having a centerfrequency of 430 nm and a bandwidth of 10 nm, and photodiodes havinginternal trans-impedance amplifiers. The electrical output signals fromthe photodiodes were transmitted onto a National Instruments signalboard and processed by a customized Labview application. The eightsamples had the following eight relative concentrations: 0.0, 0.2, 0.4,0.6, 0.8, 1.0, 1.2, and 1.4.

FIG. 14 shows the absorbance measurements taken from the NationalInstruments board according to this experimental use of the invention.Each of the eight depicted waveforms corresponds to the output signal ofone of the eight photodiodes. Each of the waveforms settles near a valuethat corresponds to the measured absorbance of the corresponding fluidsample.

FIG. 15 shows a line plot of these absorbances, set forth on thevertical axis, as a function of the concentration of the samples, setforth on the horizontal axis. Also shown is a line of best fit, derivedthrough a linear regression. As shown, the absorbance satisfies anear-linear relationship with the concentration, as desired. Thecoordinates of the plotted points are set forth below in Table 1.

TABLE 1 Channel 1 2 3 4 5 6 7 8 Conc. 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Abs.0.009 0.060 0.121 0.177 0.235 0.302 0.355 0.417

In one aspect, the detection system 800 described above, which includesseparate detection components for each detecting window 814, is aninexpensive and portable alternative to commercially availablespectrometers. However, the detection system 800 results in little or noperformance loss.

FIG. 16, by way of comparison, shows sample plots of absorbance as afunction of concentration. The plot labeled with squares is for acommercially available spectrometer, and the plot labeled with trianglesis for the detection system 800 described herein. As shown, the plotsare substantially similar, and in particular both plots very closelyalign with their linear best fits, which are plotted but not visiblesince they align so closely with their corresponding plots.

FIG. 17 shows sample plots wherein the fluidic samples have lowerconcentrations. Again the plot labeled with squares corresponds to thecommercially available spectrometer, while the plot labeled withdiamonds corresponds to the detection system 800 described herein. Asshow, at these lower concentrations the detection system 800 produces aplot that more closely aligns with its line of best fit than does thecommercially available spectrometer. Thus, at lower concentrations thedetection system 800 may offer superior performance.

As mentioned above, the microfluidic chip 104 described above generallyincludes a top substrate 232, a bottom substrate 230, and a membrane 238disposed therebetween. The microfeatures (e.g., pumps, valves, orreservoirs) are fabricated in one or more of the top substrate 232, thebottom substrate 230, and the membrane 238. In certain embodiments, thetop substrate 232, the bottom substrate 230, and the membrane 238 areall made of plastic. Exemplary materials include non-elastomericpolymers, such as polymethyl methacrylate, polystyrene, polycarbonate,and acrylic. These materials are beneficial at least in part becausethey are reasonably rigid, which is suitable for the top substrate 232and the bottom substrate 230. Moreover, these materials can bedeformable when used in thin layers, which is suitable for the membrane238 which, as mentioned above with respect to FIGS. 3A-B, deflectstowards and away from the top substrate 232 to close and open the valve,respectively.

In certain methods of fabrication, the top substrate 232 and themembrane 238 are laminated together, and similarly the membrane 238 andthe bottom substrate 230 are laminated together. While any laminationmethod known in the art may be used, in one aspect of the inventionthese layers are laminated by: 1) using a weak solvent bonding agent,and 2) laminating the layers under mild conditions, such as under lowheat or low pressure. This is beneficial at least in part because thislamination method reduces or eliminates damage to the microfeaturesduring the lamination process. More particularly, in an exemplary use,the weak solvent bonding agent is applied to one or both surfaces to beadhered, and then mild pressure (e.g., from moderate heat or moderatephysical pressure pressing the surfaces together) adheres the surfaces.

According to an aspect, the weak solvent bonding agent may be chemicallydefined as:

where, R1=H, OH or R, where R=alkyl, or is absent, R2=H, OH or R, whereR=alkyl, or is absent, and R2=H, OH or R, where R=alkyl, or is absent.

Alternatively, the weak solvent may have a chemical formula of:

where R1=H, OH or R, where R=alkyl, or is absent, and R2=H, OH or R,where R=alkyl, or is absent.

Alternatively, the weak solvent may have a chemical formula of:

where R1=H, OH or R, where R=alkyl, or is absent.

In a particular aspect, the weak solvent bonding agent is acetonitrile.Acetonitrile is a versatile solvent that is widely used in analyticalchemistry and other applications. It is 100% miscible with water andexhibits excellent optical properties. The ability of acetonitrile tohave little or no effect on polymeric surfaces under ambient conditionsbut adhere the surfaces under moderate pressure makes it highly suitablefor laminating polymeric materials such as polystyrene, polycarbonate,acrylic and other linear polymers. For example, microstructures disposedon a polystyrene substrate that was treated with acetonitrile at roomtemperature for at least several minutes did not exhibit any noticeablefeature damage.

While some materials may be more susceptible to damage from acetonytrilethan polystyrene, this increased susceptibility can be controlled byapplying the acetonitrile at a lower temperature or, alternatively, byusing a combination of acetonitrile and other inert solvents.

An additional benefit of acetonitrile-based lamination is that theprocess allows substrate alignment for structures containingmulti-component layers or fluid networks constructed utilizing both acover plate and a base plate. Unlike conventional strong solventlamination, which tends to penetrate the polymeric surface and create atacky bonding surface within seconds of solvent application,acetonitrile at room temperature can gently soften the surface. When twosurfaces with acetonitrile disposed thereon are placed in contact atlower temperature prior to applying pressure, an operator can slide thetwo surfaces against each other to adjust their alignment. Afteraligning the surfaces, the operator can then apply pressure to thesurfaces to laminate them together.

The top substrate 232, the bottom substrate 230, or the diaphragm 238may include shallow microfeatures which may interfere with the bonding.More particularly, the bottom substrate 230 may include microfeatureshaving a depth on the order of about 5 .mu.m or less, and a lateralwidth of more than about 1 mm. Since the membrane 238 may be deformable,any pressure applied to the surfaces during the bonding process maydeflect the membrane 238 into the shallow microfeature and inadvertentlybond the membrane 238 to the bottom of the microfeature. In order toprevent this, certain exemplary fabrication methods include selectivelyapplying the weak solvent bonding agent so that the bonding agent is notpresent in areas where bonding should not occur.

As disclosed above, the acetonitrile bonding agent may require thermalactivation to create a bond between the polymeric components. Theheating can be provided in a number of ways. When the heat is applied tothe components by positioning them on a heat source, the heat must beconducted through the components to the bonding interface.

Another method is referred to herein as solvent-assisted microwavebonding. In this method the substrate components are prepared forbonding as previously disclosed. However, instead of heating the bulkstructure by contacting a high temperature source, the assembledcomponent pair is exposed to microwave energy. The microwaves energy ispredominately absorbed by the polar solvent molecules without affectingthe bulk plastic component structure, thus heating the bonding interfacewithout bulk heating of the substrates. This method is particularlyuseful in situations where the heating area needs to be surfacerestricted. Alternatively, the structure to be bonded or laminated bythe weak solvent bonding agent may be cooled prior to weak solventapplication. Specifically, acetonitrile solvent lamination and bondingcan be used to fabricate diaphragms that can be used as valve and pumpstructures.

The use of the terms “a” and “an” and “the” and similar references inthe context of describing the invention (especially in the context ofthe following claims) are to be construed to cover both the singular andthe plural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening.

The recitation of ranges of values herein are merely intended to serveas a shorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein, is intended merely to better illuminateembodiments of the invention and does not impose a limitation on thescope of the invention unless otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementas essential to the practice of the invention.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the appended claims.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus, itis intended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

We claim:
 1. A microfluidic system, comprising: a modular microfluidicchip having a given configuration of microfeatures including a pluralityof diaphragm valves, each of which is actuated by a pneumatic signaldisposed in relation to only a single surface of the chip, wherein themicrofluidic chip comprises only a single polymeric substrate having theplurality of microfeatures disposed in a surface thereof and a singlepolymeric membrane attached to the surface of the substrate; a separate,modular replaceable chip manifold having a plurality of only pneumaticports on an underside thereof and a plurality of only pneumatic channelsdisposed therein in fluid connection with both the plurality of valvesand the plurality of pneumatic ports, wherein said plurality ofpneumatic ports have a fixed configuration, and said plurality ofpneumatic channels have a given configuration specifically correspondingto the given configuration of the plurality of valves, removablyconnected to the microfluidic chip; and a separate, modular pneumaticmanifold having a plurality of apertures that provide a passage of thepneumatic signal therethrough, in fluid connection with said pluralityof pneumatic ports, wherein said plurality of apertures have a fixedconfiguration specifically corresponding to the fixed configuration ofthe plurality of pneumatic ports of the chip manifold, removablyconnected to the chip manifold, wherein the modular replaceable chipmanifold is disposed in between and in direct contact with the modularmicrofluidic chip and the modular pneumatic manifold, and themicrofluidic system is a reconfigurable system due to the modularmicrofluidic chip, the separate, modular replaceable chip manifold, andthe separate, modular pneumatic manifold.
 2. The microfluidic system ofclaim 1, wherein the separate, modular replaceable chip manifold furtherincludes a seal disposed on an upper surface thereof that interfaceswith the membrane.
 3. The microfluidic system of claim 1, furthercomprising a reservoir removably disposed on the microfluidic chip. 4.The system of claim 1, wherein the chip manifold includes at least oneset of the pneumatic channels fluidly connected to only a singleaperture of the pneumatic manifold.
 5. The system of claim 4, whereinthe at least one set of pneumatic channels comprises: a single pneumaticchannel for routing the pneumatic signal from the aperture to aplurality of pneumatic channels branching from the single channel,wherein the plurality of channels branching from the single channelroute the pneumatic signal to respective ones of the plurality ofvalves.
 6. The system of claim 4, wherein the at least one set ofpneumatic channels consists of a single pneumatic channel.
 7. Themicrofluidic system of claim 1, further comprising a controller forcontrolling the pneumatic signals being transmitted through theplurality of apertures.
 8. The microfluidic system of claim 7, whereinthe plurality of apertures have respective pneumatic transducers thatfluidly couple to the plurality of apertures for transmitting thepneumatic signals through the plurality of apertures, and the controlleris adapted to transmit electronic signals that individually actuate therespective pneumatic transducers in a sequence according to logicinstructions from the controller.
 9. The microfluidic system of claim 8,wherein the pneumatic transducers comprise solenoids.
 10. Themicrofluidic system of claim 8, wherein at least one of the pneumatictransducers includes: an output port for transmitting a pneumaticpressure, and a switch for selecting the pneumatic pressure as one of apositive pressure and a negative pressure based on at least one of theelectronic signals.
 11. The microfluidic system of claim 10, wherein thepneumatic pressure is generated by a diaphragm pump coupled to theoutput port, wherein the diaphragm pump is DC-powered and has a sizethat facilitates portability of the microfluidic system.
 12. Themicrofluidic system of claim 1, wherein the pneumatic manifold includesa plurality of laminated layers.
 13. The microfluidic system of claim 1,wherein the pneumatic manifold further comprises attachment ports forcoupling the pneumatic transducers to the pneumatic manifold.
 14. Themicrofluidic system of claim 1, wherein the plurality of apertures haverespective pneumatic transducers that fluidly couple to the plurality ofapertures, the pneumatic manifold includes at least one positivepressure source and at least one negative pressure source, and the atleast one positive pressure source and the at least one negativepressure source fluidly couple to the pneumatic transducers.
 15. Themicrofluidic system of claim 14, wherein the at least one positivepressure source provides signals corresponding to a first state ofbinary logic communicated to the pneumatic transducers from acontroller, and the at least one negative pressure source providessignals corresponding to a second state of binary logic communicatedfrom a controller to the pneumatic transducers.
 16. The microfluidicsystem of claim 1, wherein the microfluidic chip includes at least onemicrofluidic pump, and the microfluidic pump includes three or more ofthe plurality of valves.
 17. The microfluidic system of claim 1, whereinthe microfluidic chip includes a plurality of fluidic assay channels fortransporting and reacting fluidic reagents.
 18. The microfluidic systemof claim 1, further comprising an optical detection system for analyzingfluidic samples in the micro fluidic chip.
 19. The microfluidic systemof claim 1, wherein each of the pneumatic manifold, the chip manifold,and the microfluidic chip are a non-elastomer plastic material.
 20. Themicrofluidic system of claim 19, wherein the non-elastomer plasticmaterial comprises at least one of polymethyl methacrylate, polystyrene,polycarbonate, and acrylic.